/*******************************************************************************
 * Copyright (c) 2000, 2006 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.runtime;

/**
 * <code>Assert</code> is useful for for embedding runtime sanity checks
 * in code. The predicate methods all test a condition and throw some
 * type of unchecked exception if the condition does not hold.
 * <p>
 * Assertion failure exceptions, like most runtime exceptions, are
 * thrown when something is misbehaving. Assertion failures are invariably
 * unspecified behavior; consequently, clients should never rely on
 * these being thrown (and certainly should not being catching them
 * specifically).
 * </p><p>
 * This class can be used without OSGi running.
 * </p><p>
 * This class is not intended to be instantiated or sub-classed by clients.
 * </p>
 * @since org.eclipse.equinox.common 3.2
 */
public final class Assert {
    /* This class is not intended to be instantiated. */
    private Assert() {
        // not allowed
    }

    /** Asserts that an argument is legal. If the given boolean is
     * not <code>true</code>, an <code>IllegalArgumentException</code>
     * is thrown.
     *
     * @param expression the outcode of the check
     * @return <code>true</code> if the check passes (does not return
     *    if the check fails)
     * @exception IllegalArgumentException if the legality test failed
     */
    public static boolean isLegal(boolean expression) {
        return isLegal(expression, ""); //$NON-NLS-1$
    }

    /** Asserts that an argument is legal. If the given boolean is
     * not <code>true</code>, an <code>IllegalArgumentException</code>
     * is thrown.
     * The given message is included in that exception, to aid debugging.
     *
     * @param expression the outcode of the check
     * @param message the message to include in the exception
     * @return <code>true</code> if the check passes (does not return
     *    if the check fails)
     * @exception IllegalArgumentException if the legality test failed
     */
    public static boolean isLegal(boolean expression, String message) {
        if (!expression)
            throw new IllegalArgumentException(message);
        return expression;
    }

    /** Asserts that the given object is not <code>null</code>. If this
     * is not the case, some kind of unchecked exception is thrown.
     * 
     * @param object the value to test
     */
    public static void isNotNull(Object object) {
        isNotNull(object, ""); //$NON-NLS-1$
    }

    /** Asserts that the given object is not <code>null</code>. If this
     * is not the case, some kind of unchecked exception is thrown.
     * The given message is included in that exception, to aid debugging.
     *
     * @param object the value to test
     * @param message the message to include in the exception
     */
    public static void isNotNull(Object object, String message) {
        if (object == null)
            throw new AssertionFailedException("null argument:" + message); //$NON-NLS-1$
    }

    /** Asserts that the given boolean is <code>true</code>. If this
     * is not the case, some kind of unchecked exception is thrown.
     *
     * @param expression the outcode of the check
     * @return <code>true</code> if the check passes (does not return
     *    if the check fails)
     */
    public static boolean isTrue(boolean expression) {
        return isTrue(expression, ""); //$NON-NLS-1$
    }

    /** Asserts that the given boolean is <code>true</code>. If this
     * is not the case, some kind of unchecked exception is thrown.
     * The given message is included in that exception, to aid debugging.
     *
     * @param expression the outcode of the check
     * @param message the message to include in the exception
     * @return <code>true</code> if the check passes (does not return
     *    if the check fails)
     */
    public static boolean isTrue(boolean expression, String message) {
        if (!expression)
            throw new AssertionFailedException("assertion failed: " + message); //$NON-NLS-1$
        return expression;
    }
}
